Biology: The Pholcidae is the ninth largest spider family of the world encompassing ca 969 species and 81 genera. They range in size from very small to medium-sized (1-10 mm body size), usually with long legs that may exceed 60 mm in some species. The species occupy a wide range of habitats and are found all over the world except for some islands and arctic regions. In recent decades synanthropic species in particular have gradually increased their range in the cooler, temperate regions. Pholcus phalangioides serves as an example and is now almost cosmopolitan in distribution. This species inhabit houses in most parts of the world and since it is independent of the climate outdoors it will probably continue to increase its range given there are heated buildings to occupy and enough prey to feed on during the cold season. Other synanthropic species that have increased their range in Europe include Crossopriza lyoni and Holocnemus pluchei. Perhaps global warming has influenced the spread, which mainly have taken place in recent years. Also the species Pholcus opilionoides occurring in natural and semi-natural habitats has increased its range northwards in Europe. Pholcids build three-dimensional messy, irregular, tangled webs in which they hang inverted on the under surface of the web. The webs are often constructed in dark and damp niches such as buildings and cellars, in caves, behind loose bark, in cavities between boulders, under rocks and other objects on the ground and in burrows. The web has no viscid properties but the criss-cross structure delay the escape of insects entangled in the web. The spider quickly advance to wrap its prey in silk and when securely wrapped the spider is able to inflict the fatal bite without any risk. Some species feed on other spiders even of their own kin. In my house I have observed Pholcus phalangioides to prey on spiders of its own species and large, stout species such as Amaurobius similis and Scotophaeus blackwalli. The species is also known to prey on other common house spiders of the northern temperate regions such as species of Tegenaria. I once interrupted the capture of a Salticus scenius female before the fatal bite. The salticid was completely wrapped in silk but nevertheless able to bite its way out and escape still going strong. If food is scarce some pholcids will leave their web and invade the webs of other spiders with the purpose of eating the host, the eggs, or the prey. They vibrate the web to mimic the struggle of trapped prey as an attempt to lure the host of the web to approach, unaware of it will be attacked. This is very much similar to the technique used by the pirate spiders (Mimetidae). When a pholcid is threatened the spider will spin itself in small circles so rapidly that the contours of the spider becomes blurred or almost invisible. This behaviour is possibly an effort to minimize the chance of it falling prey to predators passing by. If the spider continues to feel threatened it may drop from the web and walk away in an unsteady, wobbling fashion. Despite the clumsy pace it is nevertheless able to climb vertical surfaces. After the mating the female sits inverted in her web carrying her eggs in her chelicerae. The eggs are loosely held together by a few strands of silk. The male will often stay nearby the female until he dies. Females often live for more years than males and may mate again with another male. After hatching the spiderlings are either carried by the female for a few days where after they stay in the web guarded by the female. Eventually they will disperse to start a life on their own. The three northern European genera are easily separated by the shape and colour of their abdomens which is long and tubular in Pholcus and Holocnemus but globular in Psilochorus. The two former genera are distinguished by the colour of the ventral side of their abdomens which is light in the two Pholcus species, but black in Holocnemus pluchei.

Characters of family: The pholcids belong to the group of araneomorph, ecribellate spider families having 6 or 8 eyes and 3 tarsal claws. The anterior medials are smallest or absent in six-eyed species. The secondary eyes are arranged in two triads, which in some species are placed on tubercles. Other diagnostic characters for the family include the high, often concave clypeus of about the same height as the chelicerae and the usually very long legs with long and flexible tarsi with many pseudosegments. The carapace is subcircular with the head region often raised. In some species fovea is well developed. The sternum is convex often with sinuous sides, broadly truncated at rear. The chelicers are relatively weak and fused along the greater part of length. Males often have the chelicerae armed with teeth-like outgrowths. The labium is wider than long and fused with sternum. The female palp is small, slender and is not provided with a claw or tooth. The shape of the abdomen varies from globose to elongated cylindrical. The most common colours of the abdomen range between pale grey and darker brownish-grey. Psilochorus simoni has a bluish-green or blue abdomen. In some species a cardiac mark is clearly visible while in others this mark is just faintly darker than the ground colour of the abdomen. Many species also possess darker chevrons, bandings or blotches mainly in the midline of the abdomen. The abdomen of Holocnemus pluchei is reticulated very much like a giraffe. In some genera the spinners are situated ventrally and moved forward to a position near the epigastric furrow. There is no tracheal spiracle. Despite being haplogyne, pholcids do have the internal female genitalia protected by an epigyne like sclerotization. These are rather variable and allow pholcids to be identified from drawings of epigynes with the same ease as entelegyne spiders. The male palp is very complex having swollen palp segments and a large paracymbium.